Chemoenzymatic synthesis of multivalent neoglycoconjugates carrying the helminth glycan antigen LDNF

MALDI-TOF mass spectrometry as a diagnostic tool in human and veterinary helminthology: a systematic review

Background

Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MS) has become a widely used technique for the rapid and accurate identification of bacteria, mycobacteria and certain fungal pathogens in the clinical microbiology laboratory. Thus far, only few attempts have been made to apply the technique in clinical parasitology, particularly regarding helminth identification.

Methods

We systematically reviewed the scientific literature on studies pertaining to MALDI-TOF MS as a diagnostic technique for helminths (cestodes, nematodes and trematodes) of medical and veterinary importance. Readily available electronic databases (i.e. PubMed/MEDLINE, ScienceDirect, Cochrane Library, Web of Science and Google Scholar) were searched from inception to 10 October 2018, without restriction on year of publication or language. The titles and abstracts of studies were screened for eligibility by two independent reviewers. Relevant articles were read in full and included in the systematic review.

Results

A total of 84 peer-reviewed articles were considered for the final analysis. Most papers reported on the application of MALDI-TOF for the study of Caenorhabditis elegans, and the technique was primarily used for identification of specific proteins rather than entire pathogens. Since 2015, a small number of studies documented the successful use of MALDI-TOF MS for species-specific identification of nematodes of human and veterinary importance, such as Trichinella spp. and Dirofilaria spp. However, the quality of available data and the number of examined helminth samples was low.

Conclusions

Data on the use of MALDI-TOF MS for the diagnosis of helminths are scarce, but recent evidence suggests a potential role for a reliable identification of nematodes. Future research should explore the diagnostic accuracy of MALDI-TOF MS for identification of (i) adult helminths, larvae and eggs shed in faecal samples; and (ii) helminth-related proteins that are detectable in serum or body fluids of infected individuals.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3493-9) contains supplementary material, which is available to authorized users.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update for 2009-2010

This review is the sixth update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2010. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, arrays and fragmentation are covered in the first part of the review and applications to various structural typed constitutes the remainder. The main groups of compound that are discussed in this section are oligo and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Many of these applications are presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis.

Glycosyltransferases in chemo-enzymatic synthesis of oligosaccharides

Many oligosaccharides are not commercially available, which limits studies focused on elucidation of glycan functions; therefore chemo-enzymatic methods to synthesize them can be very useful. Here, we describe the procedure to synthesize the Galα1-3GalNAcβ1-4GlcNAcβ-R (Gal-LDN) moiety, containing the Galα1-3GalNAc epitope found on the parasitic helminth Haemonchus contortus. An acceptor substrate providing a terminal N-acetylglucosamine was prepared by coupling the fluorescent hydrophobic aglycon, 2,6-diaminopyridine (DAP), to N,N'-diacetylchitobiose. By the subsequent action of recombinant Caenorhabditis elegans β1,4-N-acetylgalactosaminyltransferase the substrate was efficiently converted to GalNAcβ1-4GlcNAcβ-R (LDN-R). Since no recombinant α1,3-galactosyltransferase has been described that acts on terminal βGalNAc, we used bovine α1,3-galactosyltransferase to obtain a partial conversion of LDN-R to the Gal-LDN antigen. This method can be applied to synthesize any oligosaccharide, provided that specific glycosyltransferases are available, or related enzymes that can be pushed to elongate the selected acceptor.

Glycan microarray profiling of parasite infection sera identifies the LDNF glycan as a potential antigen for serodiagnosis of trichinellosis

Diagnostic methods for parasite infections still highly depend on the identification of the parasites by direct methods such as microscopic examination of blood, stool and tissue biopsies. Serodiagnosis is often carried out to complement the direct methods; however, few synthetic antigens with sufficient sensitivity and specificity are available. Here we evaluated a glycan microarray approach to select for synthetic glycan antigens that could be used for serodiagnosis of parasitic infections. Using a glycan array containing over 250 different glycan antigens, we identified GalNAcβ1-4(Fucα1-3)GlcNAc-R (LDNF) as a glycan antigen that is recognized by antibodies from Trichinella-infected individuals. We synthesized a neoglycoconjugate, consisting of five LDNF molecules covalently coupled to bovine serum albumin (BSA), and used this neoglycoconjugate as an antigen to develop a highly sensitive total-Ig ELISA for serological screening of trichinellosis. The results indicate that glycan microarrays constitute a promising technology for fast and specific identification of parasite glycan antigens to improve serodiagnosis of different parasitic infections, either using an ELISA format, or parasite-specific glycan arrays.